Method of capactively coupling energy to an electrosurgical instrument

ABSTRACT

In the present invention, a surgical trocar is adapted to capacitively couple electrosurgical energy to specially adapted cordless electrosurgical instruments. In one embodiment of the present invention, an electrosurgical trocar includes a cannula, a capacitive electrosurgical adapter and a locking connector adapted to connect the cannula to the capacitive electrosurgical adapter. The cannula is an elongated tube which may be inserted into a body cavity, duct or vessel. The electrosurgical adapter includes a housing with an elongated central aperture, an adapter proximal capacitor plate and an adapter distal capacitor plate positioned in and extending axially along the elongated aperture, first and second electrical conductors, first and second external conductors, a compression mechanism, an outer housing and an electrical cord.

This is a divisional application of U.S. Ser. No. 08/885,458, filed Jun.30, 1997.

This application is related to the following copending applications:application Ser. No. 08/856,534, filed May 14, 1997; application Ser.No. 08/877,715, filed Jun. 18, 1997; application Ser. No. 08/878,421,filed Jun. 18, 1997; application Ser. No. 08/884,949, filed Jun. 30,1997; application Ser. No. 08/885,166, filed Jun. 30, 1997; andapplication Ser. No. 08/885,517, filed Jun. 30, 1997, which applicationsare hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates, in general, to an improvedelectrosurgical trocar and method of use and, more particularly, to anelectrosurgical trocar adapted to capacitively couple electrosurgicalenergy to specially adapted cordless electrosurgical instruments.

BACKGROUND OF THE INVENTION

The surgical trocar has become the mainstay in the development andacceptance of endoscopic surgical procedures. Endoscopic surgeryinvolves the performance of surgery through a number of openings havinga relatively small diameter. These openings are made with the trocar,which typically includes a trocar obturator and a trocar cannula. Theobturator is the piercing implement which punctures the body wall tomake the opening. Once the puncture is made, the obturator is withdrawnfrom the cannula. The cannula then provides a small diameter passagewayinto and through the body wall to provide access for additional surgicalinstrumentation to the surgical site. The function, structure andoperation of a typical trocar is described in detail in U.S. Pat. No.5,387,197, which is hereby incorporated herein by reference.

Such additional surgical instruments may include, for example, bipolaror monopolar electrosurgical instruments which utilize radio frequencyelectrosurgical energy. Known electrosurgical instruments include, forexample, bipolar forceps, bipolar scissors, monopolar-hooks,monopolar-scissors and, bipolar endocutters. Each of those instrumentshas an electrosurgical end effector which is adapted to treat tissuethrough the application of electrosurgical (e.g. radio frequency or RF)energy to tissue which is brought in contact with the electrosurgicalend effector. Most known electrosurgical instruments are connected byelectrical cords to electrosurgical generators. The structure andoperation of a typical bipolar cutter/stapler (“bipolar endocutter”) isdescribed in U.S. Pat. No. 5,403,312 which is hereby incorporated hereinby reference.

Electrosurgical generators, such as the Force II generator (which isavailable from Valleylab of Bolder Colo.), supply electrical energy tothe electrosurgical instruments through electrical cords. The electricalcords, being attached directly to the electrosurgical instrument, maymake the electrosurgical instrument inconvenient to use. Alternatively,electrical cords may cause undesirable delays as one electrosurgicalinstrument is unplugged from the generator and another is plugged in.Thus, it would be advantageous to design a cordless electrosurgicalinstrument. However, such a cordless electrosurgical instrument wouldhave to be connected to the electrosurgical generator through somealternate arrangement. Therefore, it would also be advantageous todesign a trocar or a trocar adapter which is adapted to capacitivelycouple electrosurgical energy to specially designed cordlesselectrosurgical instruments. It would further be advantageous to designan electrosurgical instrument and electrosurgical trocar or trocaradapter wherein the electrosurgical energy is capacitively coupled fromthe electrosurgical trocar to the electrosurgical instrument whenelectrosurgical energy is applied to the electrosurgical trocar ortrocar adapter.

SUMMARY OF THE INVENTION

In the present invention, a surgical trocar is adapted to capacitivelycouple electrosurgical energy to specially adapted cordlesselectrosurgical instruments. In one embodiment of the present invention,an electrosurgical trocar includes a cannula, a capacitiveelectrosurgical adapter and a locking connector adapted to connect thecannula to the capacitive electrosurgical adapter. The cannula is anelongated tube which may be inserted into a body cavity, duct or vessel.The electrosurgical adapter includes a housing with an elongated centralaperture, a proximal capacitor plate and a distal capacitor platepositioned in and extending axially along the elongated aperture, firstand second electrical conductors, first and second external conductors,a compression mechanism, an outer housing and an electrical cord.

In a further embodiment of the present invention, the adapter apertureis formed by an aperture wall positioned in the adapter housing. Theadapter proximal and distal capacitor plates are positioned in andextend axially along the aperture, forming at least a portion of thewalls of the aperture. The first and second electrical conductorsconnect the adapter proximal and adapter distal capacitor plates to thefirst and second external connectors. The compression mechanism biasesthe adapter proximal and adapter distal capacitor plates toward thecenter of the adapter aperture. An electrical cord is connected to thefirst and second external connectors such that the electrical cord maybe used to plug the adapter into a suitable electrosurgical generator.

In a further embodiment of the present invention, the adapter proximalcapacitor plate is positioned in and substantially surrounds a firstportion of the adapter aperture. The adapter distal capacitor plate ispositioned in and substantially surrounds the a second portion of theadapter aperture distal to the portion of the aperture substantiallysurrounded by the adapter proximal capacitor plate. The adapter proximalcapacitor plate and the adapter distal capacitor plate are electricallyisolated and are separated by an insulation region which substantiallysurrounds the aperture between the adapter proximal capacitor plate andthe adapter distal capacitor plate. The proximal capacitor plate and thedistal capacitor plate may be separated from the aperture by a region ofdielectric material.

In a further embodiment of the present invention, the adapter proximalcapacitor plate is divided into at least a first proximal stator plateand a second proximal stator plate. The proximal stator plates beingelectrically connected such that the proximal stator plates areelectrically common. The adapter distal capacitor plate is divided intoat least a first distal stator plate and a second distal stator plate.The distal stator plates being electrically connected such that thedistal stator plates are electrically common. In a further embodiment ofthe present invention, the compression member includes one or morecompression rings positioned around the proximal stator plates and oneor more compression rings positioned around the distal stator plates. Ina further embodiment of the present invention, the stator plates areseparated from the aperture by a dielectric region which is adapted toinsulate the stator plates and to enhance capacitive of the statorplates to an electrosurgical instrument inserted into the adapter.

In a further embodiment of the present invention, the electrosurgicaltrocar includes a locking connector which connects the cannula to thecapacitive electrosurgical adapter. In this embodiment of the invention,the adapter includes first and second locking cleats extending from thedistal end of the connector. The cannula includes receptors such asindentations or ribs which hold the distal ends of the locking cleats inplace, thus holding the connector in contact with the cannula. In afurther embodiment of the present invention, the capacitiveelectrosurgical adapter is integrated into and made a part of the trocarcannula.

In a further embodiment of the present invention, each of the capacitorplates comprises an electrically conductive plate covered by a layer ofhigh dielecteric material. The high dielectric material may be composed,at least in part, of a durable high dielectric material such as BariumTitanate (BaTiO₃) or other suitable material.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. The invention itself, however, both as toorganization and methods of operation, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription, taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of a capacitive electrosurgical trocaraccording to the present invention.

FIG. 1A is a perspective view of a capacitive electrosurgical trocaraccording to the present invention including a portion of the closuretube of a capacitive electrosurgical instrument shown positioned in thecentral aperture of the capacitive electrosurgical trocar.

FIG. 2 is a plan view section taken along 2—2 in FIG. 1 through thecapacitive electrosurgical trocar illustrated in FIG. 1.

FIG. 2A is a plan view section taken along 2A—2A in FIG. 1A through thecapacitive electrosurgical trocar and closure tube illustrated in FIG.1A.

FIG. 3 is a perspective view in plane section of the capacitiveelectrosurgical adapter illustrated in FIG. 1.

FIG. 3A is a perspective view in plane section of the capacitiveelectrosurgical adapter and closure tube illustrated in FIG. 1A.

FIG. 4 is a section view taken along line 4—4 of FIG. 2.

FIG. 4A is a section view taken along line 4A—4A of FIG. 2A.

FIG. 5 is a perspective view of a cordless capacitive electrosurgicalinstrument according to the present invention.

FIG. 6A is a cutaway view of the end effector of the capacitiveelectrosurgical instrument illustrated in FIG. 5.

FIG. 6B is a cutaway view of a portion of the closure tube of thecapacitive electrosurgical instrument illustrated in FIG. 5

FIG. 7 is a cutaway view of an alternative embodiment of a portion ofthe closure tube of the capacitive electrosurgical instrumentillustrated in FIG. 5.

FIG. 8 is a schematic diagram graphically illustrating the capacitivecoupling between a capacitive electrosurgical trocar or trocar adapterand a capacitive electrosurgical instrument according to the presentinvention.

FIG. 9 is a schematic diagram graphically illustrating the capacitivecoupling between a capacitive electrosurgical trocar or trocar adapterand an alternative embodiment of a capacitive electrosurgicalinstrument.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a capacitive electrosurgical trocar 11according to the present invention. FIG. 1A is a perspective view ofcapacitive electrosurgical trocar 11 including a portion of closure tube50 of capacitive electrosurgical instrument 16. Capacitiveelectrosurgical trocar 11 includes trocar cannula 8 and a capacitiveelectrosurgical adapter 14. Capacitive electrosurgical trocar 11 mayalso include an obturator assembly (not shown) such as the oneillustrated in U.S. Pat. No. 5,387,197, which has been previouslyincorporated herein by reference. Trocar cannula 8 includes cannulahousing 12 and cannula tube 10, extending from cannula housing 12.Capacitive electrosurgical adapter 14 includes an adapter housing 15,locking connector 17 and an electric cord 18. In the embodiment of theinvention illustrated in FIG. 1, capacitive electrosurgical adapter 14is connected to trocar cannula 8 by locking connector 17. Lockingconnector 17 includes locking cleats 20 and release buttons 22. It willbe apparent that capacitive electrosurgical adapter 14 may be integrateddirectly into trocar cannula housing 12, thus eliminating the need forlocking connector 17.

FIG. 2 is a plan view section taken along 2—2 in FIG. 1 throughcapacitive electrosurgical trocar 11. FIG. 2A is a plan view sectiontaken along 2A—2A in FIG. 1A through capacitive electrosurgieal trocar11 and a portion of closure tube 50 of capacitive electrosurgicalinstrument 16. In FIGS. 2 and 2A, cannula housing 12 includes flappervalve 34, valve spring 35 and ring gasket 33. Capacitive electrosurgicaladapter 14 includes central aperture 19, front flange 25 and base flange24. Central aperture 19 is an elongated aperture for receiving workinginstruments such as endoscopic electrosurgical instruments. Capacitiveelectrosurgical adapter 14 further includes a plurality of capacitorplates which, in the embodiment illustrated in FIGS. 2-4, compriseproximal capacitor plate 28 and distal capacitor plate 29. At least aportion of the interior wall of central aperture 19 is formed by upperinsulator 30 and lower insulator 31. Upper insulator 30 and lowerinsulator 31 together comprise trocar insulator 134. Upper insulator 30and lower insulator 31 are positioned against front flange 25 and baseflange 24. Compression member 32 is, in the present embodiment, ano-ring which is positioned outside of upper insulator 30 and lowerinsulator 31 to bias upper insulator 30 and lower insulator 31 towardthe center of central aperture 19. Compression member 32 may also be,for example, a spring, a flexible sleeve, a plurality of o-rings or anyother suitable biasing member. Proximal capacitor plate 28 and distalcapacitor plate 29, being positioned in upper insulator 30 and lowerinsulator 31 in the embodiments of FIGS. 1-4 are likewise biased towardthe center of central aperture 19 by compression member 32. Latchdetents 4 in cannula housing 12, are adapted to receive locking cleats20 of locking connector 17.

FIG. 3 is a perspective view in plane section of capacitiveelectrosurgical adapter 14. FIG. 3A is a perspective view in planesection of capacitive electrosurgical adapter 14 and a portion ofclosure tube 50 of electrosurgical instrument 16. Referring now to FIGS.2-4 and 2A-4A and particularly to FIGS. 3 and 3A, capacitiveelectrosurgical adapter 14 includes adapter housing 15, locking cleats20, base flange 24, front flange 25 and release buttons 22. Upperinsulator 30 and lower insulator 31 are positioned in capacitiveelectrosurgical adapter 14 and are held in place by base flange 24 andfront flange 25. Compression members 32 bias upper insulator 30 andlower insulator 31 toward the center of central aperture 19. Upperinsulator 30 and lower insulator 31 are preferably constructed of a highdielectric material such as Barium Titanate (BaTiO₃). Proximal capacitorplate 28 comprises first proximal capacitor stator plate 128 and secondproximal capacitor stator plate 130. Distal capacitor plate 29 comprisesfirst distal capacitor stator plate 129 and second distal capacitorstator plate 131. Electrosurgical energy is supplied to capacitiveelectrosurgical trocar 11 by electric cord 18 which is connected tobipolar electrosurgical plug 64. Electric cord 18 is electricallyconnected to upper conductor 36 and lower conductor 38. Upper conductor36 is electrically connected to upper stator tab 26 which iselectrically connected to first proximal capacitor stator plate 128.Conductor 136 electrically connects upper stator tab 26 to lower statortab 27 which is electrically connected to second proximal capacitorstator plate 130. Lower conductor 38 is electrically connected to lowerstator tab 127 which is electrically connected to second distalcapacitor stator plate 131. Conductor 138 electrically connects lowerstator tab 127 to upper stator tab 126 which is electrically connectedto first distal capacitor stator plate 129. Thus, electrosurgical energymay be coupled from bipolar electrosurgical plug 64 to each of proximalcapacitor plate 28 and distal capacitor plate 29. Proximal capacitorplate 28 and distal capacitor plate 29 are positioned in, andelectrically insulated from one another by trocar insulator 134. Inparticular, first proximal capacitor stator plate 128 and first distalcapacitor stator plate 129 are positioned in upper insulator 30 whichalso insulates first proximal capacitor stator plate 128 from firstdistal capacitor stator plated 129. Further, second proximal capacitorstator plate 130 and second distal capacitor stator plate 131 arepositioned in lower insulator 31 which also insulates second proximalcapacitor stator plate 130 from second distal capacitor stator plated131. Compression member 32 surrounds upper insulator 30 and lowerinsulator 31. First proximal dieletric region 151 comprises the portionof upper insulator 30 positioned between first proximal capacitor statorplate 128 and central aperture 19. Second proximal dilectric region 152comprises the portion of lower insulator 31 positioned between secondproximal capacitor stator plate 130 and central aperture 19. Firstdistal dielectric region 153 comprises the portion of upper insulator 30positioned between first distal capacitor stator plate 129 and centralaperture 19. Second distal dielectric region 154 comprises the portionof lower insulator 31 positioned between second distal capacitor statorplate 131 and central aperture 19.

FIG. 4 is a sectional view of capacitive electrosurgical adapter 14taken along line 4—4 of FIG. 2. FIG. 4A is a section view of capacitiveelectrosurgical adapter 14 taken along line 4A—4A of FIG. 2A. Referringnow to FIGS. 2-4 and particularly to FIGS. 4 and 4A, central aperture 19is defined by aperture interior wall 21. The portion of apertureinterior wall 21 visible in FIG. 4 is formed, at least in part, by firstinsulator surface 60 of upper insulator 30 and insulator surface 61 oflower insulator 31. Compression member 32, which comprises two o-ringsin the embodiment of FIGS. 2-4, biases upper insulator 30 and lowerinsulator 31 toward the center of central aperture 19. Electric cord 18is connected to first proximal capacitor stator plate 128 of proximalcapacitor plate 28 by upper conductor 36 and upper stator tab 26. Upperstator tab 26 is connected to lower stator tab 27 by conductor 136.Electric cord 18 is connected to second distal capacitor stator plate131 of distal capacitor plate 29 by lower conductor 38 and lower statortab 27. As illustrated particularly in FIGS. 2 and 3, Upper stator tab126 is connected to lower stator tab 127 by conductor 138. Base flange24 and front flange 25, which are part of adapter housing 15, hold upperinsulator 30 and lower insulator 31 in place, thus positioning proximalcapacitor plate 28 and distal capacitor plate 29 around central aperture19. Strain relief 23 protects electric cord 18 as it passes throughadapter housing 15. Although proximal capacitor plate 28 is illustratedas being visible in FIGS. 4 and 4A, it will be apparent that proximalcapacitor plate 28 is shown as being visible for convenience indescribing the invention and would actually be hidden.

FIG. 5 is a perspective view of a capacitive cordless electrosurgicalinstrument 16 which may be, for example, a bipolar cutter/stapler. InFIG. 5, capacitive electrosurgical instrument 16 includes handle 72,closure tube 50 and bipolar end effector 57. Closure tube 50 iselongated to facilitate insertion of end effector 57 through a trocarcannula, thus facilitating the use of capacitive electrosurgicalinstrument 16 in endoscopic or laparoscopic surgical procedures. Handle72, which is located at the proximal end of capacitive electrosurgicalinstrument 16, includes grasping trigger 74, firing trigger 76 andrelease trigger 78. Closure tube 50, which connects handle 72 to endeffector 57, includes rotation knob 70. End effector 57, which islocated at the distal end of closure tube 50 includes anvil 58,cartridge channel 88 and staple cartridge 68. Capacitive electrosurgicalinstrument 16 is similar in structure and operation to the bipolarendoscopic electrocautery linear cutting and stapling instrumentillustrated and described in U.S. Pat. No. 5,403,312, which has beenpreviously incorporated herein by reference. However capacitiveelectrosurgical instrument 16 is cordless and electrosurgical energy iscapacitively coupled into electrosurgical instrument 16. In captiveelectrosurgical instrument 16, electrosurgical energy is supplied toinstrument 16 through capacitive plates which may be located in closuretube 50.

FIG. 6A is a cutaway view of end effector 57 of capacitive cordlesselectrosurgical instrument 16. FIG. 6B is a cutaway view of a portion ofclosure tube 50 of capacitive cordless electrosurgical instrument 16.FIG. 7 is a cutaway view of an alternate embodiment of a portion ofclosure tube 50 of capacitive cordless electrosurgical instrument 16. Inthe embodiments of electrosurgical instrument 16 illustrated in FIGS.6A, 6B and 7, anvil base 73 of Anvil 58 supports electrode assembly 52and includes anvil guide 65 and staple forming slots (not shown).Electrode assembly 52 is electrically coupled to first electrodeconductor 48 and to anvil electrodes 55. Anvil base 73 is insulated fromelectrode assembly 52 by anvil insulator 59. First electrode conductor48 is electrically connected to instrument proximal capacitor plate 42.Instrument proximal capacitor plate 42 is positioned in the proximalportion of closure tube 50. Channel 88 of end effector 57 supportsstaple cartridge 68, wedge guide 80 and wedge block assembly 82. Channel88 extends into and, being constructed of electrically conductivematerial, is electrically coupled to instrument distal capacitor plate43 which is positioned in the distal portion of closure tube 50. Thus,channel 88 may provide a return path for electrical energy coupled toanvil electrodes 55 of end effector 57 when end effector 57 is used tograsp tissue or other electrically conductive material and thatelectrically conductive material touches both channel 88 and anvilelectrodes 55. Electrosurgical energy coupled to channel 88 may becoupled back to electrosurgical trocar 11 through instrument distalcapacitor plate 43. Instrument proximal capacitor plate 42 iselectrically insulated from Instrument distal capacitor plate 43 byclosure tube insulator 44. Closure tube 50 also supports and enclosesthe proximal end of anvil 58, the proximal end of channel 88, firing rod84, the proximal end of knife 90, channel retainer 86 and at least aportion of wedge block assembly 82 and wedge guide 80. Closure tube 50may preferably be constructed of a durable high dielectric insulatingmaterial such as, for example, Barium Titanate (BaTiO₃). Anvil 58 opensand closes by, for example, pivoting around one or more pivot pins (notshown). In the embodiment illustrated in FIG. 7, matching inductor 49may be used to improve the efficiency of energy transfer to tissuegrasped by end effector 57. The structure and operation of themechanical features of electrosurgical instrument 16 may be betterunderstood with reference to the mechanical cutting and staplinginstrument illustrated and described in U.S. Pat. No. 5,597,107 which ishereby incorporated herein by reference.

FIG. 8 is a schematic diagram graphically illustrating the capacitivecoupling between capacitive electrosurgical trocar 11 and capacitiveelectrosurgical instrument 16. In FIG. 8, Proximal capacitor 142comprises proximal capacitor plate 28, trocar insulator 134, closuretube 50 and instrument proximal capacitor plate 42. More particularly,proximal capacitor 142 comprises first proximal capacitor stator plate128, first proximal dielectric region 151, second proximal capacitorstator plate 130, second proximal dielectric region 152, a portion ofthe proximal end of closure tube 50, and instrument proximal capacitorplate 42. Distal capacitor 143 comprises distal capacitor plate 29,trocar insulator 134, closure tube 50 and instrument distal capacitorplate 43. More particularly, distal capacitor 143 comprises first distalcapacitor stator plate 129, first distal dielectric region 153, seconddistal capacitor stator plate 131, second distal dielectric region 154,a portion of the distal end of closure tube 50 and instrument distalcapacitor plate 43.

In FIGS. 8 and 9, first output 6 of electrosurgical generator 5 isconnected to proximal capacitor plate 28 of proximal capacitor 142through cord 18 and upper conductor 36. Second output 7 ofelectrosurgical generator 5 is connected to distal capacitor plate 29 ofdistal capacitor 143 through cord 18 and lower conductor 38. When endeffector 57 is closed around electrically conductive material such asbiological tissue, the electrical circuit from instrument proximalcapacitor plate 42 of proximal capacitor 142 to instrument distalcapacitor plate 43 of distal capacitor 143 is completed. Thus, with endeffector 57 closed around conductive material and electrosurgicalgenerator 5 turned on, electrosurgical energy, such as electricalcurrent at a predetermined output frequency and power, passes fromelectrosurgical generator 5, through proximal capacitor 142, to endeffector 57 and returns through distal capacitor 143 and back to secondoutput 7 of electrosurgical generator 5.

As FIGS. 8 and 9 schematically illustrate, instrument proximal capacitorplate 42 and instrument distal capacitor plate 43 are elongated so thatmovement of electrosurgical instrument 16 does not result in loss ofcapacitive coupling in capacitors 142 and 143. Thus, even as theinstrument is moved within trocar 11 to facilitate treatment of thepatient, capacitive coupling may be maintained. The circuit illustratedin FIG. 9 includes a matching inductor 49 which may be used toelectrically match capacitive electrosurgical instrument 16 tocapacitive electrosurgical trocar 11 in order to increase the powercoupled to the tissue grasped by end effector 57. In particular,inductor 49 would be selected to make the load represented by thetrocar, instrument and tissue appear to be substantially resistive atthe frequency of interest.

In operation, trocar cannula 8 is used with a conventional trocarorbitor (not shown) to penetrate the wall of a body cavity such as, forexample, the abdominal wall of a human being. After the body wall ispenetrated, the obturator assembly is withdrawn from trocar cannula 8,and the cannula is used as an access portal for the passage of variousendoscopic instruments to provide, for example, access to the internalorgans of a human being. Where the endoscopic instrument to be used is acordless capacitive electrosurgical instrument such as electrosurgicalinstrument 16, capacitive electrosurgical adapter 14 may be attached totrocar cannula 8. Once capacitive electrosurgical adapter 14 is attachedto trocar cannula 8 and electric cord 18 is attached to a suitableelectrosurgical generator (such as generator 5 in FIG. 8), capacitiveelectrosurgical trocar 11 may be used to provide electrosurgical energyto cordless capacitive electrosurgical instruments such aselectrosurgical instrument 16. When a cordless capacitiveelectrosurgical instrument such as electrosurgical instrument 16, isinserted into a body cavity through, for example, capacitiveelectrosurgical trocar 11, end effector 57 passes through trocar cannula8 and into the body cavity while most of closure tube 50 remains introcar 11. Handle 72, which is outside of capacitive electrosurgicaltrocar 11, may be manipulated by the surgeon to control the position ofend effector 57.

A cordless capacitive bipolar electrosurgical instrument according tothe present invention, such as electrosurgical instrument 16 of FIG. 5may be used by inserting the cordless instrument into an appropriatecapacitive electrosurgical trocar such as the electrosurgical trocarillustrated in FIG. 1. In the capacitive electrosurgical trocarillustrated in FIG. 1, electrosurgical energy is provided to instrument16 by, for example, the capacitive coupling between proximal capacitorplate 28 of trocar 11 and instrument proximal capacitor plate 42 ofinstrument 16. An electrical return path is provided by, for example,the capacitive coupling between distal capacitor plate 29 of trocar 11and instrument distal capacitor plate 43 of instrument 16. The diameterof central aperture 19 generally corresponds with the outer diameter ofclosure tube 50 so that closure tube 50 slides through central aperture19 and the interior of cannula tube 10. Electrical coupling will bemaintained so long as capacitor plates 42 and 43 are positioned incentral aperture 19 opposite capacitor plates 28 and 29 to formcapacitors 142 and 143. Upper insulator 30 and lower insulator 31 formtrocar insulator 134. Closure tube 50 and trocar insulator 134, beingpreferably formed of a material having a high dielectric constant, actas the dielectric for proximal capacitor 142 and distal capacitor 143which are illustrated schematically in FIG. 8. Compression member 32helps to ensure that trocar insulator 134 and closure tube 50 maintaingood physical contact, minimizing any air gap and enhancing capacitivecoupling between the plates of proximal capacitor 142 and the plates ofdistal capacitor 143. Capacitive electrical coupling may be enhanced byusing multiple capacitors in capacitive electrosurgical trocar 11. Withinstrument capacitor plates 42 and 43 positioned opposite capacitorplates 28 and 29, electrosurgical energy may be supplied to instrument16 through electric cord 18 and capacitive electrosurgical trocar 11. Inthe embodiments of the invention illustrated herein, electrosurgicalenergy supplied to trocar 11 by cord 18 passes through conductors 36,38, 136 and 138 to stator tabs 26, 126, 27 and 127 and capacitor plates28 and 29 into electrosurgical instrument 16 via instrument capacitorplates 42 and 43. Electrosurgical energy supplied to electrosurgicalinstrument 16 via instrument capacitor plates 42 and 43 may be suppliedto end effector 57 via the circuit formed by instrument proximalcapacitor plate 42, conductor 48, electrode assembly 52, cartridgechannel 88 and instrument distal capacitor plate 43. This circuit iscompleted when biological tissue or other conductive material is graspedby end effector 57, providing a path from electrode assembly 52 tocartridge channel 88. In electrosurgical instrument 16, cartridgechannel 88 and anvil electrode 55 are electrically conductive. Thus,where electrode assembly 52 acts as a primary electrode, cartridgechannel 88 acts as a secondary or return electrode. When electricallyconductive tissue is grasped by end effector 57 and an electrosurgicalgenerator is connected to first instrument proximal capacitor plate 42and second instrument distal capacitor plate 43, electrosurgical energywill flow through the grasped tissue, coagulating the grasped tissueprovided that capacitive electrosurgical instrument 16 is positioned introcar 11 as described herein. It may also be advantageous to provideone or more switches to control the flow of electrical current to trocar11 or to end effector 57 of instrument 16.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. Accordingly, it isintended that the invention be limited only by the spirit and scope ofthe appended claims.

What is claimed is:
 1. A method of supplying electrosurgical energy to acordless capacitive electrosurgical instrument, wherein said methodcomprises the steps of: a) inserting said cordless capacitiveelectrosurgical instrument into a capacitive electrosurgical adapter; b)connecting said capacitive electrosurgical adapter to a source ofelectrosurgical energy; and c) turning on said source of electrosurgicalenergy.
 2. A method of supplying electosurgical energy to a cordlesscapacitive electrosurgical instrument through a capacitiveelectrosurgical adapter, wherein said capacitive electosurgical adaptercomprises; an elongated central aperture extending from a first end ofsaid adapter to a second end of said adapter, wherein said centralaperture is surrounded by an aperture wall; an input capacitor plate andan output capacitor plate positioned in and extending axially along saidelongated aperture; a first electrical conductor connected to said inputcapacitor plate; a second electrical conductor connected to said outputcapacitor plate; a compression mechanism structurally connected to saidinput capacitor plate and said output capacitor plate, wherein saidcompression mechanism is adapted to bias said input capacitor plate andsaid output capacitor plate toward a central axis of said aperture; anouter housing surrounding said aperture and said input and outputcapacitor pates; and an electrical cord connected to said first andsecond electrical connectors and extending from said outer housing; saidmethod comprising the steps of: inserting said cordless capacitiveelectrosurgical instrument into said elongated aperture; and supplyingelectrosurgical energy to said input capacitor plate and said outputcapacitor plate through said first and second electrical conductors. 3.A method of supplying electrosurgical energy to a cordless capacitiveelectrosurgical instrument through a capacitive electrosurgical trocarwherein said capacitive electrosurgical trocar comprises: a cannula; anelectrosurgical adapter connected to said cannula wherein saidelectrosurgical adapter comprises: first and second capacitor platesarranged around an opening in an interior portion of said adapter; afirst electrical conductor connecting said first capacitor plate to afirst connector; and a second electrical conductor connecting saidsecond capacitor plate to a second connector. said method comprising thesteps of: inserting said cordless capacitive electrosurgical instrumentinto said electrosurgical adapter and said cannula; and supplyingelectrosurgical energy to said first and second capacitor plates throughsaid first and second connectors.
 4. A method of transmittingelectrosurgical energy from a capacitive electrosurgical adapter to acordless capacitive electrosurgical instrument, wherein said methodcomprising the steps of: coupling electrosurgical energy into first andsecond capacitive plates in said capacitive electrosurgical adapter;placing said cordless capacitive electrosurgical instrument in saidcapacitive electrosurgical adapter; and positioning first and secondcapacitive plates of said cordless capacitive electrosurgical instrumentadjacent said first and second capacitive plates of said electrosurgicaladapter.